DESCRIPTION: The overall objective of this application is to investigate the relationship between the morphology and architectural configuration of both trabecular and cortical bone and their mechanical properties. These investigations are directed towards extending the applicant's capabilities for future testing of a global hypothesis that bone cells sense mechanical stimulus through hierarchical extracellular matrix deformations. The long term goal is to characterize the specific nature of the mechanical factors which stimulate bone cells to respond. The present application, an extension of previous work, proposes to develop experimental and analytical studies to estimate stress and strain distributions at the osteocyte lacunae level. Specifically, the specific aims are to correlate the trabecula and cortical bone mechanical properties with structural morphology, bone age, and spatial location within the bone; assess the error in the experimental and theoretical measurements; and estimate the strain distributions around osteocyte lacunae.